What is a Prolactin Test?

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A prolactin (PRL) test measures how much of a hormone called prolactin you have in your blood. The hormone is made in your pituitary gland, which is located just below your brain.

When women are pregnant or have just given birth, their prolactin levels increase so they can make breast milk. But it’s possible to have high prolactin levels if you’re not pregnant, and even if you’re a man.

Your doctor may order a prolactin test when you report having the following symptoms:

How the Test Is Done

You don’t need to make any special preparations for a prolactin test. You will get a blood sample taken at a lab or a hospital. A lab worker will insert a needle into a vein in your arm to take out a small amount of blood.

Some people feel just a little sting. Others might feel moderate pain and see slight bruising afterwards.

After a few days, you’ll get the results of your prolactin test in the form of a number.

The normal range for prolactin in your blood are:

Males: 2 to 18 nanograms per milliliter (ng/mL)

Nonpregnant females: 2 to 29 ng/mL

Pregnant females: 10 to 209 ng/mL

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If Your Prolactin Levels Are High

If your value falls outside the normal range, this doesn’t automatically mean you have a problem. Sometimes the levels can be higher if you’ve eaten or were under a lot of stress when you got your blood test.

Also, what’s considered a normal range may be different depending on which lab your doctor uses.

If your levels are very high -- up to 1,000 times the upper limit of what’s considered normal -- this could be a sign that you have prolactinoma. This tumor is not cancer, and it can be treated with medicine. In this case, your doctor may want you to get an MRI.

You’ll lie inside a magnetic tube as the MRI device uses radio waves to put together a detailed image of your brain. It will show whether there’s a mass near your pituitary gland and, if so, how big it is.

If Your Levels Are Low

If your prolactin levels are below the normal range, this could mean your pituitary gland isn’t working at full steam. That’s known as hypopituitarism. Lower levels of prolactin usually do not need medical treatment.